Method of controlling motor grader, motor grader, and work management system for motor grader

ABSTRACT

A motor grader includes a vehicular body, a blade, a front wheel located in front of the blade, two rear wheels located in the rear of the blade, a first sensor which detects a position of the vehicular body as first sensor information, a second sensor which detects an inclination of the vehicular body as second sensor information, a first swing member which rotatably supports both of the two rear wheels arranged in the front and rear relation and is swingably supported by the vehicular body, and a third sensor which detects an angle of swing of the first swing member with respect to the vehicular body as third sensor information. A method of controlling a motor grader includes obtaining the first to third sensor information and calculating positions of the rear wheels based on the obtained first to third sensor information.

TECHNICAL FIELD

The present disclosure relates to a method of controlling a motorgrader, a motor grader, and a work management system for a motor grader.

BACKGROUND ART

A motor grader has conventionally been known as a work vehicle. Themotor grader is a wheeled work vehicle which grades road surfaces orgrounds to a smooth state.

For example, US Patent Application Publication No. 2015/0197253 (PTD 1)discloses a scheme for calculating a geographical coordinate based oninformation from a plurality of sensors and showing information oncurrent topography on a display.

CITATION LIST

Patent Document

PTD 1: US Patent Application Publication No. 2015/0197253

SUMMARY OF INVENTION Technical Problem

In order to improve productivity in executing operations in aconstruction project, current topography to be worked should accuratelyand efficiently be measured, and execution of an object to be workedshould be done based on both of design topography representing a targetshape of the object to be worked and the current topography.

An object of the present invention is to provide a method of controllinga motor grader, a motor grader, and a work management system for a motorgrader capable of accurately obtaining current topography to be worked.

Solution to Problem

A motor grader according to one disclosure includes a vehicular body, ablade attached to the vehicular body, a front wheel located in front ofthe blade and attached on each of a left side and a right side of thevehicular body, two rear wheels located in the rear of the blade andarranged in front and rear relation on each of the left side and theright side of the vehicular body, a first sensor which detects aposition of the vehicular body as first sensor information, a secondsensor which detects an inclination of the vehicular body as secondsensor information, a first swing member which rotatably supports bothof the two rear wheels arranged in the front and rear relation and isswingably supported by the vehicular body, and a third sensor whichdetects an angle of swing of the first swing member with respect to thevehicular body as third sensor information. A method of controlling amotor grader includes obtaining the first to third sensor informationdetected by the first to third sensors and calculating positions of therear wheels based on the obtained first to third sensor information.

A motor grader according to one disclosure includes a vehicular body, ablade attached to the vehicular body, a front wheel located in front ofthe blade and attached on each of a left side and a right side of thevehicular body, two rear wheels located in the rear of the blade andarranged in front and rear relation on each of the left side and theright side of the vehicular body, a first sensor which detects aposition of the vehicular body as first sensor information, a secondsensor which detects an inclination of the vehicular body as secondsensor information, a first swing member which rotatably supports bothof the two rear wheels arranged in the front and rear relation and isswingably supported by the vehicular body, a third sensor which detectsan angle of swing of the first swing member with respect to thevehicular body as third sensor information, and a controller connectedto the first to third sensors. The controller obtains the first to thirdsensor information detected by the first to third sensors and calculatespositions of the rear wheels based on the obtained first to third sensorinformation.

A work management system for a motor grader according to one disclosureincludes a motor grader and a display. The motor grader includes avehicular body, a blade attached to the vehicular body, a front wheellocated in front of the blade and attached on each of a left side and aright side of the vehicular body, two rear wheels located in the rear ofthe blade and arranged in front and rear relation on each of the leftside and the right side of the vehicular body, a first sensor whichdetects a position of the vehicular body as first sensor information, asecond sensor which detects an inclination of the vehicular body assecond sensor information, a first swing member which rotatably supportsboth of the two rear wheels arranged in the front and rear relation andis swingably supported by the vehicular body, a third sensor whichdetects an angle of swing of the first swing member with respect to thevehicular body as third sensor information, a controller connected tothe first to third sensors, and a communication apparatus. Thecontroller obtains the first to third sensor information detected by thefirst to third sensors and calculates positions of the rear wheels basedon the obtained first to third sensor information. The communicationapparatus transmits data for showing an image based on comparisonbetween the positions of the rear wheels and design topography to theoutside. The display shows an image based on the data transmitted fromthe communication apparatus.

A motor grader according to one disclosure includes a vehicular bodyincluding a front frame and a rear frame pivotably coupled to the frontframe, a blade attached to the vehicular body, a front wheel located infront of the blade and attached to the vehicular body, a rear wheellocated in the rear of the blade and attached to the vehicular body, aposition sensor which is attached to the front frame and detects aposition of the front frame, an inclination sensor which is attached tothe vehicular body and detects an inclination of the vehicular body, andan angle sensor which detects an angle of pivot of the front frame withrespect to the rear frame. A method of controlling a motor graderincludes obtaining sensor information detected by the position sensor,the inclination sensor, and the angle sensor and calculating a positionof the rear wheel based on the obtained sensor information.

A motor grader according to one disclosure includes a vehicular bodyincluding a front frame and a rear frame pivotably coupled to the frontframe, a blade attached to the vehicular body, a front wheel located infront of the blade and attached to the vehicular body, a rear wheellocated in the rear of the blade and attached to the vehicular body, aposition sensor which is attached to the front frame and detects aposition of the front frame, an inclination sensor which is attached tothe vehicular body and detects an inclination of the vehicular body, anangle sensor which detects an angle of pivot of the front frame withrespect to the rear frame, and a controller connected to the positionsensor, the inclination sensor, and the angle sensor. The controllerobtains sensor information detected by the position sensor, theinclination sensor, and the angle sensor and calculates a position ofthe rear wheel based on the obtained sensor information.

Advantageous Effects of Invention

According to the method of controlling a motor grader and a motor graderin the present invention, accuracy in execution of land-grading workscan be improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view schematically showing a construction of amotor grader 1 based on an embodiment.

FIG. 2 is a side view schematically showing the construction of motorgrader 1 based on the embodiment.

FIG. 3 is a diagram illustrating overview of a construction of a pivotmechanism of motor grader 1 based on the embodiment.

FIG. 4 is a diagram illustrating overview of a construction of a swingmechanism of motor grader 1 based on the embodiment.

FIG. 5 is a block diagram showing a configuration of a control systemincluded in motor grader 1 based on the embodiment.

FIG. 6 is a flowchart illustrating a scheme for motor grader 1 based onthe embodiment to obtain current topography.

FIG. 7 is a diagram illustrating a scheme for calculating positions ofrear wheels of motor grader 1 based on the embodiment.

FIG. 8 is a diagram illustrating an image shown on a display 160 ofmotor grader 1 based on the embodiment.

FIG. 9 is a conceptual diagram of a work management system based on athird modification of the embodiment.

FIG. 10 is a flowchart illustrating a scheme for motor grader 1 based onthe third modification of the embodiment to obtain current topography.

DESCRIPTION OF EMBODIMENTS

A motor grader according to an embodiment will be described below. Thesame elements have the same reference characters allotted in thedescription below and their labels and functions are also the same.Therefore, detailed description thereof will not be repeated.

<A. Appearance>

FIG. 1 is a perspective view schematically showing a construction of amotor grader 1 based on an embodiment.

FIG. 2 is a side view schematically showing the construction of motorgrader 1 based on the embodiment.

As shown in FIGS. 1 and 2, motor grader 1 in the embodiment mainlyincludes running wheels 11 and 12, a vehicular body frame 2, a cab 3,and a work implement 4. Motor grader 1 includes components such as anengine arranged in an engine compartment 6. Work implement 4 includes ablade 42. Motor grader 1 can do such works as land-grading works, snowremoval works, light cutting, and mixing of materials with blade 42.

Running wheels 11 and 12 include a front wheel 11 and a rear wheel 12.Though FIGS. 1 and 2 show running wheels six in total which consist oftwo front wheels 11 one on each side and four rear wheels 12 two on eachside, the number of front wheels 11 and rear wheels 12 and arrangementthereof are not limited thereto.

Front wheel 11 is located in front of blade 42 and attached on each of aleft side and a right side of vehicular body frame 2.

Rear wheels 12 include two wheels located in the rear of blade 42 andarranged in front and rear relation on each of the left side and theright side of vehicular body frame 2. By way of example, FIG. 2 shows afront-side rear wheel 12A and a rear-side rear wheel 12B of left rearwheels 12.

The rear wheels are provided with a tandem apparatus 50A (a first swingmember) rotatably supporting both of the two rear wheels arranged in thefront and rear relation and swingably supported by vehicular body frame2. A central point of swing P of tandem apparatus 50A is shown by way ofexample.

In the description of the drawings below, a direction in which motorgrader 1 travels in straight lines is referred to as a fore/aftdirection (X) of motor grader 1. In the fore/aft direction of motorgrader 1, a side where front wheel 11 is arranged with respect to workimplement 4 is defined as the fore direction. In the fore/aft directionof motor grader 1, a side where rear wheel 12 is arranged with respectto work implement 4 is defined as the aft direction. A lateral directionof motor grader 1 is a direction orthogonal to the fore/aft direction ina plan view. A right side and a left side in the lateral direction (Y)in facing front are defined as a right direction and a left direction,respectively. An upward/downward direction (Z) of motor grader 1 is adirection orthogonal to the plane defined by the fore/aft direction andthe lateral direction. A side in the upward/downward direction where theground is located is defined as a lower side and a side where the sky islocated is defined as an upper side.

The fore/aft direction refers to a fore/aft direction of an operator whosits at an operator's seat in cab 3. The lateral direction refers to alateral direction of the operator who sits at the operator's seat. Thelateral direction refers to a direction of a vehicle width of motorgrader 1. The upward/downward direction refers to an upward/downwarddirection of the operator who sits at the operator's seat. A directionin which the operator sitting at the operator's seat faces is defined asthe fore direction and a direction behind the operator sitting at theoperator's seat is defined as the aft direction. A right side and a leftside at the time when the operator sitting at the operator's seat facesfront are defined as the right direction and the left direction,respectively. A foot side of the operator who sits at the operator'sseat is defined as a lower side, and a head side is defined as an upperside.

Vehicular body frame 2 includes a rear frame 21, a front frame 22, andan exterior cover 25. Rear frame 21 supports exterior cover 25 andcomponents such as the engine arranged in engine compartment 6. Exteriorcover 25 covers engine compartment 6. Exterior cover 25 is provided withan upper opening 26, a lateral opening 27, and a rear opening. Upperopening 26, lateral opening 27, and the rear opening are provided topass through exterior cover 25 in a direction of thickness.

Rear frame 21 supports exterior cover 25 and components such as theengine arranged in engine compartment 6. Exterior cover 25 covers enginecompartment 6. For example, each of four rear wheels 12 is attached torear frame 21 as being rotatably driven by driving force from theengine.

Front frame 22 is attached in front of rear frame 21. Front frame 22 ispivotably coupled to rear frame 21. Front frame 22 extends in thefore/aft direction. Front frame 22 includes a base end portion coupledto rear frame 21 and a tip end portion opposite to the base end portion.Front frame 22 includes a front end. The front end is included in thetip end portion of front frame 22. For example, two front wheels 11 arerotatably attached to the tip end portion of front frame 22.

A counter weight 51 is attached to the front end of front frame 22 (or afront end of vehicular body frame 2). Counter weight 51 represents onetype of attachments to be attached to front frame 22. Counter weight 51is attached to front frame 22 in order to increase a downward load to beapplied to front wheel 11 to allow steering and to increase a pressingload on blade 42.

Cab 3 is carried on front frame 22. In cab 3, an operation portion (notshown) such as a steering wheel, a gear shift lever, a lever forcontrolling work implement 4, a brake, an accelerator pedal, and aninching pedal is provided. Cab 3 may be carried on rear frame 21.

Work implement 4 mainly includes a draw bar 40, a swing circle 41, blade42, a hydraulic motor 49, and various hydraulic cylinders 44 to 48.

Draw bar 40 has a front end portion swingably attached to the tip endportion of front frame 22. Draw bar 40 has a rear end portion supportedon front frame 22 by a pair of lift cylinders 44 and 45. As a result ofextending and retracting of the pair of lift cylinders 44 and 45, therear end portion of draw bar 40 can move up and down with respect tofront frame 22. Therefore, as lift cylinders 44 and 45 both retract, aheight of blade 42 with respect to front frame 22 is adjusted in theupward direction. As lift cylinders 44 and 45 both extend, a height ofblade 42 with respect to front frame 22 is adjusted in the downwarddirection.

Draw bar 40 is vertically swingable with an axis along a direction oftravel of the vehicle being defined as the center, as a result ofextending and retracting of lift cylinders 44 and 45.

A draw bar shift cylinder 46 is attached to front frame 22 and a sideend portion of draw bar 40. As a result of extending and retracting ofdraw bar shift cylinder 46, draw bar 40 is movable laterally withrespect to front frame 22.

Swing circle 41 is revolvably (rotatably) attached to the rear endportion of draw bar 40. Swing circle 41 can be driven by hydraulic motor49 as being revolvable clockwise or counterclockwise with respect todraw bar 40 when viewed from above the vehicle. As swing circle 41 isdriven to revolve, a blade angle of blade 42 is adjusted.

Blade 42 is arranged between front wheel 11 and rear wheel 12. Blade 42is arranged between the front end of vehicular body frame 2 (or thefront end of front frame 22) and a rear end of vehicular body frame 2.Blade 42 is supported on swing circle 41. Blade 42 is supported on frontframe 22 with swing circle 41 and draw bar 40 being interposed.

Blade 42 is supported as being movable in the lateral direction withrespect to swing circle 41. Specifically, a blade shift cylinder 47 isattached to swing circle 41 and blade 42 and arranged along alongitudinal direction of blade 42. With blade shift cylinder 47, blade42 is movable in the lateral direction with respect to swing circle 41.Blade 42 is movable in a direction intersecting with a longitudinaldirection of front frame 22.

Blade 42 is supported as being swingable around an axis extending in thelongitudinal direction of blade 42 with respect to swing circle 41.Specifically, a tilt cylinder 48 is attached to swing circle 41 andblade 42. As a result of extending and retracting of tilt cylinder 48,blade 42 swings around the axis extending in the longitudinal directionof blade 42 with respect to swing circle 41, so that an angle ofinclination of blade 42 with respect to the direction of travel of thevehicle can be changed.

A position detection sensor 64 is arranged on an upper ceiling of cab 3.Position detection sensor 64 includes an antenna for real timekinematic-global navigation satellite systems (RTK-GNSS) and a globalcoordinate computer.

An inertial measurement unit (IMU) 66 is arranged on the upper ceilingof cab 3. IMU 66 detects an inclination of vehicular body frame 2. Inthe embodiment, IMU 66 detects an angle of inclination θ2 with respectto the lateral direction of vehicular body frame 2 (see FIG. 7 (B)) andan angle of inclination θ1 with respect to the fore/aft direction ofvehicular body frame 2 (see FIG. 7 (A)). IMU 66 updates angle ofinclination θ1 and angle of inclination θ2, for example, in a period of100 Hz.

<B. Mechanism>

FIG. 3 is a diagram illustrating overview of a construction of a pivotmechanism of motor grader 1 based on the embodiment.

As shown in FIG. 3, front frame 22 and rear frame 21 are coupled to eachother with a vertical central pin 30. Specifically, front frame 22 ispivotably coupled to rear frame 21 at a position substantially below cab3. Front frame 22 pivots with respect to rear frame 21 as a result ofextending and retracting of an articulation cylinder 32 coupled betweenfront frame 22 and rear frame 21 based on an operation of a controllever in cab 3. By bending (articulating) front frame 22 with respect torear frame 21, a slewing radius at the time of revolution of motorgrader 1 can be smaller and works for excavating a groove and cutting aslope by offset running can be done. Offset running refers to lineartravel of motor grader 1 by setting a direction of bending of frontframe 22 with respect to rear frame 21 and a direction of revolution offront wheel 11 with respect to the front frame to directions opposite toeach other. An articulation angle detection sensor 60 is attached torear frame 21, and the articulation angle detection sensor detects anangle of articulation representing an angle of bending of front frame 22with respect to rear frame 21. When front frame 22 is located at aneutral position with respect to rear frame 21, an angle of articulationis defined as 0°.

FIG. 4 is a diagram illustrating overview of a construction of a swingmechanism of motor grader 1 based on the embodiment.

FIG. 4 shows two rear wheels 12A and 12B on the left side and two rearwheels 12C and 12D on the right side with respect to vehicular bodyframe 2. Rear wheels 12A and 12B are arranged in front and rearrelation. Rear wheels 12C and 12D are arranged in front and rearrelation.

Tandem apparatus 50A rotatably supporting both of rear wheels 12A and12B and swingably supporting both of rear wheels 12A and 12B withrespect to vehicular body frame 2 and a tandem apparatus 50B rotatablysupporting both of rear wheels 12C and 12D and swingably supporting bothof rear wheels 12C and 12D with respect to vehicular body frame 2 areprovided.

An engine is coupled to a rear axle 58 with driving force transmissionmeans (not shown) being interposed.

Tandem apparatuses 50A and SOB are swing members and provided as beingswingable around rear axle 58.

Though not shown, rear axle 58 and shafts of rear wheels 12B and 12D areconnected to each other with the driving force transmission means beinginterposed. By driving the engine, motor grader 1 travels with rearwheels 12B and 12D functioning as driving wheels whereas rear wheels 12Aand 12C functioning as driven wheels.

In the present example, rear wheels 12 swing with tandem apparatuses 50Aand SOB being interposed in accordance with projections and recesses incurrent topography on which the motor grader travels. By providingtandem apparatuses 50A and 50B, transmission of sway due to projectionsand recesses to blade 42 through vehicular body frame 2 is prevented asmuch as possible. Motor grader 1 can thus do highly accurateland-grading works.

Tandem angle detection sensors 62A and 62B which detect a tandem angleof swing of rear wheels 12 with tandem apparatuses 50A and 50B beinginterposed are attached to tandem apparatuses 50A and 50B, respectively.

<C. System Configuration>

FIG. 5 is a block diagram showing a configuration of a control systemincluded in motor grader 1 based on the embodiment.

As shown in FIG. 5, the control system of motor grader 1 includes, byway of example, a hydraulic pump 131, a control valve 134, a hydraulicactuator 135, an engine 136, an engine controller 138, a throttle dial139, a rotation sensor 140, a potentiometer 145, a starter switch 146, amain controller 150, articulation angle detection sensor 60, tandemangle detection sensor 62, position detection sensor 64, IMU 66, adisplay 160, and a communication apparatus 170.

Hydraulic pump 131 delivers hydraulic oil used for driving workimplement 4 and the like.

Hydraulic actuator 135 is connected to hydraulic pump 131 with controlvalve 134 being interposed. Hydraulic actuator 135 includes anarticulation cylinder 32.

A swash plate drive apparatus 132 is driven based on an instruction frommain controller 150 and changes an angle of inclination of a swash plateof hydraulic pump 131.

Control valve 134 controls hydraulic actuator 135. Control valve 134 isimplemented by a proportional solenoid valve and connected to maincontroller 150. Main controller 150 outputs an operation signal(electric signal) in accordance with a direction of operation and/or anamount of operation of a work implement lever and a travel control leverto control valve 134. Control valve 134 controls an amount of hydraulicoil to be supplied from hydraulic pump 131 to hydraulic actuator 135 inaccordance with the operation signal.

Engine 136 has a driveshaft connected to hydraulic pump 131 andhydraulic pump 131 is driven in coordination with the driveshaft.

Engine controller 138 controls an operation of engine 136 in accordancewith an instruction from main controller 150. Engine 136 is implementedby a diesel engine by way of example. The number of rotations of engine136 is set through throttle dial 139 or the like, and an actual numberof rotations of the engine is detected by rotation sensor 140. Rotationsensor 140 is connected to main controller 150.

Potentiometer 145 is provided in throttle dial 139. Potentiometer 145detects a set value (an amount of operation) of throttle dial 139. Theset value of throttle dial 139 is transmitted to main controller 150.Potentiometer 145 outputs a command value for the number of rotations ofengine 136 to engine controller 138. A target number of rotations ofengine 136 is adjusted in accordance with the command value.

Engine controller 138 adjusts the number of rotations of engine 136 bycontrolling an amount of fuel injection by a fuel injection apparatus inaccordance with an instruction from main controller 150.

Starter switch 146 is connected to engine controller 138. When anoperator operates starter switch 146 (sets start), a start signal isoutput to engine controller 138 so that engine 136 starts.

Main controller 150 is a controller which controls the entire motorgrader 1 and implemented by a central processing unit (CPU), anon-volatile memory, a timer, and the like.

Though a configuration in which main controller 150 and enginecontroller 138 are separate from each other is described in the presentexample, they can also be implemented as one common controller.

Main controller 150 is connected to articulation angle detection sensor60, tandem angle detection sensor 62, position detection sensor 64, IMU66, and communication apparatus 170. Main controller 150 obtains sensorinformation and calculates positions of the rear wheels based on theobtained sensor information. Main controller 150 obtains currenttopography data based on the calculated positions of the rear wheels andhas display 160 show work support information based on comparison withdesign topography data.

Communication apparatus 170 is provided to transmit and receive datathrough a communication network to and from an external apparatus (forexample, a server). For example, information on the calculated positionsof the rear wheels may be transmitted to an external apparatus by usingcommunication apparatus 170. Work support information shown on display160 may be transmitted to an external apparatus.

<D. Control Flow>

FIG. 6 is a flowchart illustrating a scheme for motor grader 1 based onthe embodiment to obtain current topography.

Referring to FIG. 6, main controller 150 obtains sensor information(step S2). Main controller 150 obtains sensor information detected byeach of articulation angle detection sensor 60, tandem angle detectionsensor 62, position detection sensor 64, and IMU 66.

Then, main controller 150 calculates positions of the rear wheels ofmotor grader 1 (step S4). Main controller 150 calculates positions ofthe rear wheels based on sensor information detected by each ofarticulation angle detection sensor 60, tandem angle detection sensor62, position detection sensor 64, and IMU 66.

FIG. 7 is a diagram illustrating a scheme for calculating positions ofthe rear wheels of motor grader 1 based on the embodiment.

FIG. 7 (A) shows a diagram showing motor grader 1 like a model whenmotor grader 1 is viewed from above.

In the present example, a scheme for calculating positions of the rearwheels based on various types of sensor information will be described.Specifically, a position where rear wheel 12B on the left side is incontact with current topography is calculated.

By way of example, a direction of straight travel of motor grader 1 isdefined as an X direction and a direction orthogonal to the X directionis defined as a Y direction.

Cab 3 is provided on front frame 22 and a position Q0 of positiondetection sensor 64 provided on the upper ceiling of cab 3 can beobtained based on sensor information from position detection sensor 64.

A position Q1 of a rear wheel is calculated with position Q0 beingdefined as the reference coordinate.

A coordinate X0 in the X direction of position Q1 of the rear wheel withposition Q0 being defined as the reference coordinate is expressed inthe following formula:coordinate X0=X1+X2+X3where X1 represents a length between position Q0 and a position ofbending R0 and it has an already known value set in advance.

X2 is expressed in the following formula:X2=L1×cos(α1)−L2×sin(α1)where L1 represents a length between position of bending R0 and aposition of the center R1 of rear axle 58 and has an already known valueset in advance. An angle α1 represents an angle of articulation anddetected by articulation angle detection sensor 60.

X3 is expressed in the following formula:X3=L4×cos(α1)L4=L3×cos(α2)X3=L3×cos(α2)×cos(α1)where L3 represents a length between a central point of rear wheel 12Band central point of swing P and has an already known value set inadvance. An angle α2 represents a tandem angle and detected by tandemangle detection sensor 62.

Coordinate X0 in the X direction of position Q1 of the rear wheel isexpressed in the following formula based on the results of calculationabove.coordinate X0=X1+L1×cos(α1)−L2×sin(α1)+L3×cos(α2)×cos(α1)

Then, a coordinate Y0 in the Y direction of position Q1 of the rearwheel with position Q0 being defined as the reference coordinate isexpressed in the following formula.Coordinate Y0=Y1+Y2+Y3

Y1 is expressed in the following formula.Y1=L1×sin(α1)

Y2 is expressed in the following formula:Y2=L2×cos(α1)where L2 represents a length between the centerline of rear frame 21 andrear wheel 12B and has an already known value set in advance.Y3=L4×sin(α1)L4=L3αcos(α2)Y3=L3×cos(α2)×sin(α1)

Coordinate Y0 in the Y direction of position Q1 of the rear wheel isexpressed in the following formula based on the results of calculationabove.Coordinate Y0=L1×sin(α1)+L2×cos(α1)+L3×cos(α2)×sin(α1)

Then, a coordinate Z0 in a Z direction of position Q1 of rear wheel 12Bwith position Q0 being defined as the reference coordinate is expressedin the following formula:coordinate Z0=Z1+Z2+Z3where Z1 represents a length of a radius of rear wheel 12 and Z3represents a length between central point of swing P in the Z directionand position detection sensor 64. Z1 and Z3 have already known valuesset in advance.Z2=L3×sin(α2)

Coordinate Z0 in the Z direction of position Q1 of the rear wheel isexpressed in the following formula based on the results of calculationabove.Coordinate Z0=Z1+L3×sin(α2)+Z3

Coordinate X0, Y0, Z0 resulting from calculation above represents acoordinate (a vehicular body absolute coordinate) when motor grader 1 isgraded to a horizontal plane (when vehicular body frame 2 is notinclined).

FIG. 7 (B) illustrates correction of coordinate X0, Y0, Z0 of positionQ1 of the rear wheel in consideration of inclination of the vehicularbody.

As shown in the figure, motor grader 1 is inclined along currenttopography in the fore/aft direction and the lateral direction. In thepresent example, an azimuth of vehicular body frame 2 (front frame 22where position detection sensor 64 and IMU 66 are arranged) is obtainedbased on a position velocity vector (GNSS velocity vector) based onposition data from position detection sensor 64. IMU 66 detects angle ofinclination θ2 with respect to the lateral direction of vehicular bodyframe 2 and angle of inclination θ1 with respect to the fore/aftdirection of vehicular body frame 2.

A coordinate (X, Y, Z) of position Q1 of the rear wheel in considerationof the inclination is calculated in the following formula.X=X0×cos(θ1)=(X1+L1×cos(α1)−L2×sin(α1)+L3×cos(α2)×cos(α1))×cos(θ1)Y=Y0×cos(θ2)=(L1×sin(α1)+L2×cos(α1)+L3×cos(α2)×sin(α1))×cos(θ2)Z=Z0/sqrt(tan2(θ1)+tan2(θ2)+1)=(Z1+L3×sin(α2)+Z3)/sqrt(tan2(θ1)+tan2(θ2)+1)

Coordinate X, Y, Z resulting from calculation above is a globalcoordinate of the position of the rear wheel of motor grader 1 inconsideration of an inclination of the vehicular body of motor grader 1with position Q0 being defined as the reference coordinate.

Current topography data can thus be obtained in accordance with thecalculated position of the rear wheel of motor grader 1. Main controller150 obtains position Q1 of the rear wheel in the global coordinatesystem based on data on the vehicular body absolute coordinate, theposition velocity vector, and the inclination of the vehicular body.Main controller 150 converts the vehicular body absolute coordinate (alocal position) of the rear wheel into the global coordinate (a globalposition).

Referring again to FIG. 6, main controller 150 has an image shown basedon comparison between current topography data based on the calculatedposition of the rear wheel and design topography data (step S6).

Main controller 150 compares the design topography data stored inadvance in a non-volatile memory or the like with the calculated currenttopography data, and has an image based on the difference shown. Forexample, an image based on a difference in height at the same pointbetween the current topography data and the design topography data isshown.

FIG. 8 is a diagram illustrating an image shown on display 160 of motorgrader 1 based on the embodiment.

As shown in FIG. 8, together with motor grader 1, an image based on adifference in height from design topography data is shown as informationon current topography around the motor grader, which serves as worksupport information.

By way of example, various hatched regions are shown and the hatchedregions are different in type in accordance with a difference in heightat the same point between the design topography data and the currenttopography data. For example, the type may be varied between an examplein which a difference in height is great and an example in which adifference in height is small. By showing such an image, an operator canreadily recognize a difference between the current topography data andthe design topography data, and efficiency in land-grading works can beimproved.

Referring again to FIG. 6, main controller 150 determines whether or notworks have ended (step S8). When it is determined that the works haveended (YES in step S8), the process ends (end). When it is determined instep S8 that the works have not ended (NO in step S8), the processreturns to step S2. Then, the process is repeated.

Based on the scheme, current topography to be worked can accurately andefficiently be measured based on a position of the rear wheel of motorgrader 1. Then, execution works high in execution accuracy can be doneby showing an image based on the design topography data representing atarget shape of an object to be worked and the current topography data.

In particular, in the present example, current topography data isobtained based on a position of rear wheel 12 located in the rear ofblade 42. Therefore, current topography after land-grading works withblade 42 can accurately be known. Since the present scheme calculates aposition of rear wheel 12 which swings owing to tandem apparatus 50based on sensor information from tandem angle detection sensor 62,projections and recesses in current topography can accurately bemeasured and accuracy in execution can be improved.

<E. Modification>

<e1. First Modification>

An example in which a position of rear wheel 12B of motor grader 1 iscalculated is described above. Current topography data may be obtainedby calculating a position of rear wheel 12A.

Furthermore, current topography data may be obtained by calculatingpositions of rear wheels 12A and 12B.

In the present example, a scheme for calculating a position of rearwheel 12B on the left based on sensor information from tandem angledetection sensor 62A attached to tandem apparatus 50A is described.

A position of at least any one of rear wheels 12C and 12D on the rightside can also be calculated. Specifically, a position of rear wheel 12Don the right side can also be calculated with the scheme the same asabove, based on sensor information from tandem angle detection sensor62B attached to tandem apparatus 50B.

Main controller 150 obtains sensor information from articulation angledetection sensor 60, tandem angle detection sensor 62A, positiondetection sensor 64, and IMU 66 and calculates a position of rear wheel12B based on the scheme the same as described above based on theobtained sensor information, and obtains sensor information fromarticulation angle detection sensor 60, tandem angle detection sensor62B, position detection sensor 64, and IMU 66 and calculates a positionof rear wheel 12D based on the scheme the same as described above basedon the obtained sensor information.

By calculating positions of rear wheels 12B and 12D on the right sideand the left side, current topography data at two points cansimultaneously be obtained so that current topography data over a widerange can be obtained. The number of times of travel can thus bedecreased and execution works can efficiently be done.

<e2. Second Modification>

Though a construction in which cab 3 is attached to front frame 22 andposition detection sensor 64 is attached to the upper ceiling of cab 3is described above, a construction in which cab 3 is attached to rearframe 21 and position detection sensor 64 is attached to the upperceiling of cab 3 is also possible.

When cab 3 is attached to rear frame 21, relative positional relationbetween position detection sensor 64 of cab 3 provided in rear frame 21and rear wheel 12B is not varied in spite of bending of front frame 22with respect to rear frame 21.

Therefore, main controller 150 can obtain sensor information from tandemangle detection sensor 62, position detection sensor 64, and IMU 66, andcalculate a position of rear wheel 12B based on the scheme the same asdescribed above based on the obtained sensor information. Therefore,projections and recesses in current topography after land-grading workscan accurately be measured with a simplified configuration.

Though motor grader 1 includes cab 3 in the embodiment described so far,motor grader 1 does not necessarily have to include cab 3. Motor grader1 is not limited to such specifications that an operator is on boardmotor grader 1 to operate motor grader 1, but the specifications may besuch that the motor grader is operated under external remote control.Since motor grader 1 does not require cab 3 for an operator to get onboard in this case, motor grader 1 does not have to include cab 3. Whencab 3 is not provided, position detection sensor 64 and IMU 66 may bearranged on rear frame 21 or front frame 22.

<e3. Third Modification>

Though an example in which a position of rear wheel 12B of motor grader1 is calculated is described above, a result of calculation may bemanaged by an external apparatus.

FIG. 9 is a conceptual diagram of a work management system based on athird modification of the embodiment.

Referring to FIG. 9, the motor grader and an external apparatus 200 (forexample, a server) are provided to communicate with each other.

A state of motor grader 1 can be known from a remote location bytransmitting information on motor grader 1 to external apparatus 200.

By transmitting information on a position of rear wheel 12B of motorgrader 1 described above to external apparatus 200 with a display,external apparatus 200 at a remote location can accurately know currenttopography to be worked.

FIG. 10 is a flowchart illustrating a scheme for motor grader 1 based onthe third modification of the embodiment to obtain current topography.

FIG. 10 is different from the flowchart in FIG. 6 in that step S6 isreplaced with step S7.

Specifically, in step S7, main controller 150 transmits data for showingan image based on comparison between current topography data based onthe calculated position of the rear wheel and design topography data.Communication apparatus 170 transmits the data to external apparatus200.

Since the configuration is otherwise the same as described withreference to FIG. 6, detailed description will not be repeated.

According to the configuration, external apparatus 200 can obtain datafor showing an image based on comparison between current topography databased on the calculated position of the rear wheel and the designtopography data and show an image the same as described with referenceto FIG. 8 on the display.

Current topography to be worked can thus accurately be known by using adisplay of external apparatus 200 provided at a remote location.

<Function and Effect>

A motor grader according to one disclosure includes a vehicular body, ablade attached to the vehicular body, a front wheel located in front ofthe blade and attached on each of a left side and a right side of thevehicular body, two rear wheels located in the rear of the blade andarranged in front and rear relation on each of the left side and theright side of the vehicular body, a first sensor which detects aposition of the vehicular body as first sensor information, a secondsensor which detects an inclination of the vehicular body as secondsensor information, a first swing member which rotatably supports bothof the two rear wheels arranged in the front and rear relation and isswingably supported by the vehicular body, and a third sensor whichdetects an angle of swing of the first swing member with respect to thevehicular body as third sensor information. A method of controlling amotor grader includes obtaining the first to third sensor informationdetected by the first to third sensors and calculating positions of therear wheels based on the obtained first to third sensor information.

Therefore, an angle of swing of the first swing member with respect tothe vehicular body can be detected as third sensor information andpositions of the rear wheels can be calculated by using the third sensorinformation. Projections and recesses in current topography afterland-grading works can thus accurately be measured.

Preferably, the first swing member is provided for the two rear wheelsprovided on one of the left side and the right side of the vehicularbody. The motor grader further includes a second swing member which isprovided for the two rear wheels provided on the other of the left sideand the right side of the vehicular body, rotatably supports both of thetwo rear wheels arranged in the front and rear relation, and isswingably supported by the vehicular body and a fourth sensor whichdetects an angle of swing of the second swing member with respect to thevehicular body as fourth sensor information. In the calculatingpositions of the rear wheels, positions of the rear wheels provided onone of the left side and the right side of the vehicular body arecalculated based on the obtained first to third sensor information, andpositions of the rear wheels provided on the other of the left side andthe right side of the vehicular body are calculated based on theobtained first, second, and fourth sensor information.

Therefore, positions of the rear wheels provided on one of the left sideand the right side of the vehicular body are calculated based on thefirst to third sensor information, and positions of the rear wheelsprovided on the other of the left side and the right side of thevehicular body are calculated based on the first, second, and fourthsensor information. Therefore, projections and recesses in currenttopography at two points can simultaneously and accurately be measured.

Preferably, the vehicular body includes a front frame to which the frontwheel is attached and a rear frame pivotably coupled to the front frame,the rear wheels being attached to the rear frame. The first sensor isattached to the front frame. The motor grader further includes an anglesensor which detects an angle of pivot of the front frame with respectto the rear frame. In the calculating positions of the rear wheels,positions of the rear wheels are calculated based on the obtained sensorinformation and the angle of pivot.

Therefore, an angle of pivot of the front frame with respect to the rearframe is detected and positions of the rear wheels are calculated byusing the angle of pivot. Therefore, a motor grader constructed suchthat the first sensor is attached to the front frame can accuratelymeasure projections and recesses in current topography afterland-grading works.

Preferably, showing an image based on comparison between the positionsof the rear wheels and design topography is further included.

Therefore, by showing an image based on comparison between the currenttopography based on the positions of the rear wheels and the designtopography, a difference therebetween can readily be checked andefficiency in land-grading works can be improved.

Preferably, transmitting data for showing an image based on comparisonbetween the positions of the rear wheels and design topography to theoutside is further included.

Therefore, an image based on comparison between the current topographybased on the positions of the rear wheels and the design topography isshown on an external apparatus, so that a difference therebetween canreadily be checked and current topography can readily be known.

A motor grader according to one disclosure includes a vehicular body, ablade attached to the vehicular body, a front wheel located in front ofthe blade and attached on each of a left side and a right side of thevehicular body, two rear wheels located in the rear of the blade andarranged in front and rear relation on each of the left side and theright side of the vehicular body, a first sensor which detects aposition of the vehicular body as first sensor information, a secondsensor which detects an inclination of the vehicular body as secondsensor information, a first swing member which rotatably supports bothof the two rear wheels arranged in the front and rear relation and isswingably supported by the vehicular body, a third sensor which detectsan angle of swing of the first swing member with respect to thevehicular body as third sensor information, and a controller connectedto the first to third sensors. The controller obtains the first to thirdsensor information detected by the first to third sensors and calculatespositions of the rear wheels based on the obtained first to third sensorinformation.

Therefore, an angle of swing of the first swing member with respect tothe vehicular body can be detected as third sensor information andpositions of the rear wheels are calculated by using the third sensorinformation. Projections and recesses in the current topography afterland-grading works can thus accurately be measured.

Preferably, the vehicular body includes a front frame to which the frontwheel is attached and a rear frame pivotably coupled to the front frame,the rear wheels being attached to the rear frame. The first sensor isattached to the rear frame.

Therefore, according to the construction of the motor grader in whichthe first sensor is attached to the rear frame, positions of the rearwheels are calculated without using an angle of pivot of the front framewith respect to the rear frame. Therefore, projections and recesses incurrent topography after land-grading works can accurately be measuredwith a simplified configuration.

Preferably, the first swing member is provided for the two rear wheelsprovided on one of the left side and the right side of the vehicularbody. A second swing member which is provided for the two rear wheelsprovided on the other of the left side and the right side of thevehicular body, rotatably supports both of the two rear wheels arrangedin the front and rear relation, and is swingably supported by thevehicular body and a fourth sensor which detects an angle of swing ofthe second swing member with respect to the vehicular body as fourthsensor information are further provided. The controller further obtainsthe fourth sensor information detected by the fourth sensor, calculatespositions of the rear wheels provided on one of the left side and theright side of the vehicular body based on the obtained first to thirdsensor information, and calculates positions of the rear wheels providedon the other of the left side and the right side of the vehicular bodybased on the obtained first, second, and fourth sensor information.

Therefore, positions of the rear wheels provided on one of the left sideand the right side of the vehicular body are calculated based on thefirst to third sensor information, and positions of the rear wheelsprovided on the other of the left side and the right side of thevehicular body are calculated based on the first, second, and fourthsensor information. Therefore, projections and recesses in currenttopography at two points can simultaneously and accurately be measured.

Preferably, the vehicular body includes a front frame to which the frontwheel is attached and a rear frame pivotably coupled to the front frame,the rear wheels being attached to the rear frame. The first sensor isattached to the front frame. An angle sensor which detects an angle ofpivot of the front frame with respect to the rear frame is furtherprovided. The controller calculates positions of the rear wheels basedon the obtained sensor information and the angle of pivot.

Therefore, an angle of pivot of the front frame with respect to the rearframe is calculated and positions of the rear wheels are calculated byusing the angle of pivot. Therefore, a motor grader constructed suchthat the first sensor is attached to the front frame can accuratelymeasure projections and recesses in current topography afterland-grading works.

Preferably, a display which shows an image based on comparison betweenthe positions of the rear wheels and design topography is furtherprovided.

Therefore, by showing an image based on comparison between the currenttopography based on the positions of the rear wheels and the designtopography, a difference therebetween can readily be checked andefficiency in land-grading works can be improved.

Preferably, a communication apparatus which transmits data for showingan image based on comparison between the positions of the rear wheelsand design topography to the outside is further provided.

Therefore, an image based on comparison between the current topographybased on the positions of the rear wheels and the design topography isshown on an external apparatus, so that a difference therebetween canreadily be checked and current topography can readily be known.

A work management system for a motor grader according to one disclosureincludes the motor grader described above and a display which shows animage based on data transmitted from a communication apparatus.

Therefore, by showing an image based on comparison between currenttopography based on positions of the rear wheels and design topographyon the display provided separately from the motor grader, a differencetherebetween can readily be checked and current topography can readilybe known.

A motor grader according to one disclosure includes a vehicular bodyincluding a front frame and a rear frame pivotably coupled to the frontframe, a blade attached to the vehicular body, a front wheel located infront of the blade and attached to the vehicular body, a rear wheellocated in the rear of the blade and attached to the vehicular body, aposition sensor which is attached to the front frame and detects aposition of the front frame, an inclination sensor which is attached tothe vehicular body and detects an inclination of the vehicular body, andan angle sensor which detects an angle of pivot of the front frame withrespect to the rear frame. A method of controlling a motor graderincludes obtaining sensor information detected by the position sensor,the inclination sensor, and the angle sensor and calculating a positionof the rear wheel based on the obtained sensor information.

Therefore, a position of the front frame is detected by the positionsensor, an inclination of the vehicular body is detected by theinclination sensor, and an angle of pivot is detected by the anglesensor. A position of the rear wheel is calculated based on the sensorinformation. Therefore, projections and recesses in current topographyafter land-grading works can accurately be measured.

A motor grader according to one disclosure includes a vehicular bodyincluding a front frame and a rear frame pivotably coupled to the frontframe, a blade attached to the vehicular body, a front wheel located infront of the blade and attached to the vehicular body, a rear wheellocated in the rear of the blade and attached to the vehicular body, aposition sensor which is attached to the front frame and detects aposition of the front frame, an inclination sensor which is attached tothe vehicular body and detects an inclination of the vehicular body, anangle sensor which detects an angle of pivot of the front frame withrespect to the rear frame, and a controller connected to the positionsensor, the inclination sensor, and the angle sensor. The controllerobtains sensor information detected by the position sensor, theinclination sensor, and the angle sensor and calculates a position ofthe rear wheel based on the obtained sensor information.

Therefore, a position of the front frame is detected by the positionsensor, an inclination of the vehicular body is detected by theinclination sensor, and an angle of pivot is detected by the anglesensor. A position of the rear wheel is calculated based on the sensorinformation. Therefore, projections and recesses in current topographyafter land-grading works can accurately be measured.

The embodiment disclosed herein is illustrative and not restricted tothe above disclosure alone. The scope of the present application isdefined by the terms of the claims and is intended to include anymodifications within the scope and meaning equivalent to the terms ofthe claims.

REFERENCE SIGNS LIST

1 motor grader; 2 vehicular body frame; 3 cab; 4 work implement; 11front wheel; 12 rear wheel; 19 axle shaft; 21 rear frame; 22 frontframe; 40 draw bar; 41 swing circle; 42 blade; 44, 45 lift cylinder; 46draw bar shift cylinder; 47 blade shift cylinder; 48 tilt cylinder; 49hydraulic motor; 50 tandem apparatus; 51 counter weight; 60 articulationangle detection sensor; 62 tandem angle detection sensor; 64 positiondetection sensor; 66 IMU; 131 hydraulic pump; 132 swash plate driveapparatus; 135 hydraulic actuator; 136 engine; 138 engine controller;139 throttle dial; 150 main controller; and 160 display

The invention claimed is:
 1. A method of controlling a motor grader, themotor grader including a vehicular body, a blade attached to thevehicular body, a front wheel located in front of the blade and attachedon each of a left side and a right side of the vehicular body, two rearwheels located in rear of the blade and arranged in front and rearrelation on each of the left side and the right side of the vehicularbody, a first sensor which detects a position of the vehicular body asfirst sensor information, a second sensor which detects an inclinationof the vehicular body as second sensor information, a first swing memberwhich rotatably supports both of the two rear wheels arranged in thefront and rear relation and is swingably supported by the vehicularbody, a third sensor which detects an angle of swing of the first swingmember with respect to the vehicular body as third sensor information,and a controller connected to the first to third sensors, the methodcomprising: obtaining, by the controller, the first to third sensorinformation detected by the first to third sensors; and calculating, bythe controller, positions of the rear wheels based on the obtained firstto third sensor information, the calculated positions of the rear wheelsincluding a coordinate and an angle of inclination with respect to afore/aft direction of the vehicular body.
 2. The method of controlling amotor grader according to claim 1, wherein the first swing member isprovided for the two rear wheels provided on one of the left side andthe right side of the vehicular body, the motor grader further includesa second swing member which is provided for the two rear wheels providedon the other of the left side and the right side of the vehicular body,rotatably supports both of the two rear wheels arranged in the front andrear relation, and is swingably supported by the vehicular body, and afourth sensor which detects an angle of swing of the second swing memberwith respect to the vehicular body as fourth sensor information, in thecalculating positions of the rear wheels, positions of the rear wheelsprovided on one of the left side and the right side of the vehicularbody are calculated based on the obtained first to third sensorinformation, and positions of the rear wheels provided on the other ofthe left side and the right side of the vehicular body are calculatedbased on the obtained first, second, and fourth sensor information. 3.The method of controlling a motor grader according to claim 1, whereinthe vehicular body includes a front frame to which the front wheel isattached and a rear frame pivotably coupled to the front frame, the rearwheels being attached to the rear frame, the first sensor is attached tothe front frame, the motor grader further includes an angle sensor whichdetects an angle of pivot of the front frame with respect to the rearframe, and in the calculating positions of the rear wheels, positions ofthe rear wheels are calculated based on the obtained sensor informationand the angle of pivot.
 4. The method of controlling a motor graderaccording to claim 1, the method further comprising showing an imagebased on comparison between the positions of the rear wheels and designtopography.
 5. The method of controlling a motor grader according toclaim 1, the method further comprising transmitting data for showing animage based on comparison between the positions of the rear wheels anddesign topography to outside.
 6. A motor grader comprising: a vehicularbody; a blade attached to the vehicular body; a front wheel located infront of the blade and attached on each of a left side and a right sideof the vehicular body; two rear wheels located in rear of the blade andarranged in front and rear relation on each of the left side and theright side of the vehicular body; a first sensor which detects aposition of the vehicular body as first sensor information; a secondsensor which detects an inclination of the vehicular body as secondsensor information; a first swing member which rotatably supports bothof the two rear wheels arranged in the front and rear relation and isswingably supported by the vehicular body; a third sensor which detectsan angle of swing of the first swing member with respect to thevehicular body as third sensor information; and a controller connectedto the first to third sensors, the controller obtaining the first tothird sensor information detected by the first to third sensors andcalculating positions of the rear wheels based on the obtained first tothird sensor information, the calculated positions of the rear wheelsincluding a coordinate and an angle of inclination with respect to afore/aft direction of the vehicular body.
 7. The motor grader accordingto claim 6, wherein the vehicular body includes a front frame to whichthe front wheel is attached, and a rear frame pivotably coupled to thefront frame, the rear wheels being attached to the rear frame, and thefirst sensor is attached to the rear frame.
 8. The motor graderaccording to claim 6, wherein the first swing member is provided for thetwo rear wheels provided on one of the left side and the right side ofthe vehicular body, the motor grader further comprises a second swingmember which is provided for the two rear wheels provided on the otherof the left side and the right side of the vehicular body, rotatablysupports both of the two rear wheels arranged in the front and rearrelation, and is swingably supported by the vehicular body, and a fourthsensor which detects an angle of swing of the second swing member withrespect to the vehicular body as fourth sensor information, thecontroller further obtains the fourth sensor information detected by thefourth sensor, calculates positions of the rear wheels provided on oneof the left side and the right side of the vehicular body based on theobtained first to third sensor information, and calculates positions ofthe rear wheels provided on the other of the left side and the rightside of the vehicular body based on the obtained first, second, andfourth sensor information.
 9. The motor grader according to claim 6,wherein the vehicular body includes front frame to which the front wheelis attached, and a rear frame pivotably coupled to the front frame, therear wheels being attached to the rear frame, the first sensor isattached to the front frame, the motor grader further comprises an anglesensor which detects an angle of pivot of the front frame with respectto the rear frame, and the controller calculates positions of the rearwheels based on the obtained sensor information and the angle of pivot.10. The motor grader according to claim 6, the motor grader furthercomprising a display which shows an image based on comparison betweenthe positions of the rear wheels and design topography.
 11. The motorgrader according to claim 6, the motor grader further comprising acommunication apparatus which transmits data for showing an image basedon comparison between the positions of the rear wheels and designtopography to outside.
 12. A work management system for a motor gradercomprising a motor grader, the motor grader including a vehicular body,a blade attached to the vehicular body, a front wheel located in frontof the blade and attached on each of a left side and a right side of thevehicular body, two rear wheels located in rear of the blade andarranged in front and rear relation on each of the left side and theright side of the vehicular body, a first sensor which detects aposition of the vehicular body as first sensor information, a secondsensor which detects an inclination of the vehicular body as secondsensor information, a first swing member which rotatably supports bothof the two rear wheels arranged in the front and rear relation and isswingably supported by the vehicular body, a third sensor which detectsan angle of swing of the first swing member with respect to thevehicular body as third sensor information, and a controller connectedto the first to third sensors, the controller obtaining the first tothird sensor information detected by the first to third sensors andcalculating positions of the rear wheels based on the obtained first tothird sensor information, the calculated positions of the rear wheelsincluding a coordinate and an angle of inclination with respect to afore/aft direction of the vehicular body, the motor grader furtherincluding a communication apparatus which transmits data for showing animage based on comparison between the positions of the rear wheels anddesign topography to outside, and a display which shows an image basedon the data transmitted from the communication apparatus.
 13. A methodof controlling a motor grader, the motor grader including a vehicularbody including a front frame and a rear frame pivotably coupled to thefront frame, a blade attached to the vehicular body, a front wheellocated in front of the blade and attached to the vehicular body, a rearwheel located in rear of the blade and attached to the vehicular body, afirst swing member which rotatably supports the rear wheel and isswingably supported by the vehicular body, a position sensor which isattached to the front frame and detects a position of the front frame,an inclination sensor which is attached to the vehicular body anddetects an inclination of the vehicular body, an articulation anglesensor which detects an angle of pivot of the front frame with respectto the rear frame, and a tandem angle sensor which detects an angle ofswing of the first swing member that includes the rear wheel, and acontroller connected to the position sensor, the inclination sensor, thearticulation angle sensor, and the tandem angle sensor, the methodcomprising: obtaining, by the controller, sensor information detected bythe position sensor, the inclination sensor, the articulation anglesensor, and the tandem angle sensor; and calculating, by the controller,a position of the rear wheel based on the obtained sensor information,the calculated positions of the rear wheels including a coordinate andan angle of inclination with respect to a fore/aft direction of thevehicular body.
 14. A motor grader comprising: a vehicular bodyincluding a front frame and a rear frame pivotably coupled to the frontframe; a blade attached to the vehicular body; a front wheel located infront of the blade and attached to the vehicular body; a rear wheellocated in rear of the blade and attached to the vehicular body; a firstswing member which rotatably supports the rear wheel and is swingablysupported by the vehicular body; a position sensor which is attached tothe front frame and detects a position of the front frame; aninclination sensor which is attached to the vehicular body and detectsan inclination of the vehicular body; an articulation angle sensor whichdetects an angle of pivot of the front frame with respect to the rearframe; a tandem angle sensor which detects an angle of swing of thefirst swing member that includes the rear wheel, and a controllerconnected to the position sensor, the inclination sensor, thearticulation angle sensor, and the tandem angle sensor; and a controllerconnected to the position sensor, the inclination sensor, thearticulation angle sensor, and the tandem angle sensor, the controllerobtaining sensor information detected by the position sensor, theinclination sensor, the articulation angle sensor, and the tandem anglesensor, and calculating a position of the rear wheel based on theobtained sensor information, the calculated positions of the rear wheelsincluding a coordinate and an angle of inclination with respect to afore/aft direction of the vehicular body.